He practiced law in New Hampshire, first with George B. Upham, and later with David Hale. From 1828 to 1830 he practiced in Binghamton, New York, after which he returned to New Hampshire to open an office in Claremont. In 1831 Metcalf was elected Secretary of State. He held this post until 1838, when he moved to Washington, D.C. to accept a position in the Department of the Treasury while Levi Woodbury of New Hampshire was serving as Secretary. In 1840 he returned to New Hampshire and practiced law, first in Plymouth, and later in Newport. In 1845 he was appointed Register of Probate for Sullivan County. In 1848 he was appointed a trustee of the state asylum for the insane, and he served several more non-consecutive terms. He served in the New Hampshire House of Representatives from 1852 to 1853. In 1853 he served on the state commission appointed to codify New Hampshire's statutes.
Governor of New Hampshire
A member of the Democratic Party for most of his career, Metcalf later became recognized as anti-slavery and an opponent of Franklin Pierce's attempts to obtain passage of the Kansas–Nebraska Act. As a result of Metcalf's opposition to slavery, in 1855 he was nominated for Governor by the Know Nothing movement, one of the few parties with an anti-slavery plank in its platform. This effort was promoted by Free Soil Democrats including John P. Hale, who hoped to create a movement that would send New Hampshire anti-slavery activists to the United States Senate and help build the nascent Republican Party. Metcalf won the 1855 race for Governor, defeating incumbent Nathaniel B. Baker, James Bell and Asa Fowler. In 1856 he defeated John S. Wells and Ichabod Goodwin, but his margin over Wells was narrow, and the selection moved to the New Hampshire General Court, which chose Metcalf. Metcalf became identified with the Republican Party when it was founded as the major anti-slavery party in the mid 1850s. In addition to his abolitionist views, Metcalf's governorship was noteworthy for his support of a prohibition law, which passed in 1855, and remained in force until 1889. He retired after the completion of his second term, and resided in Claremont. He died in Claremont on August 26, 1858.
Family
In 1835 he married Lucretia Ann Bingham. She died a few weeks after giving birth in 1836, and the baby died soon afterwards. He married Martha Ann Gilmore in 1843, and they had two children: son Ralph ; and daughter Frances Elizabeth.